Custom hotkey for selecting edit field
I'm not sure that they actually setup a shortcut to edit the values. A background colour of green indicates that the values are keyframed but not on the current frame, while a yellow background indicates a keyframe exists on the current frame.

See below, the location is keyframed on the current frame while rotation has a keyframe on another frame.



When the mouse is over the values pressing I will insert a keyframe for the values at the current frame. You can also right click and choose Insert Keyframes, you also have options to Delete (only current frame) or Clear (all frames)  Keyframes.

Clicking in the centre of a number field will enter edit mode allowing you to type in the value to use.